1. Field of the Invention
The invention relates to electrical powerline carrier channel testing, and refers more specifically to an electronic programmable powerline carrier channel testing structure and method. 2.
Description of the Prior Art
In large electrical power transmission systems, such as those operated by many public utilities, serious faults and/or overloads are sensed at strategic positioned electrical power transmission stations. Such power stations typically include line terminal relays operable to automatically cut-off a powerline and/or reroute electrical energy around an overloaded or faulted powerline to facilitate continued power transmission to the extent possible. Signals between power transmission stations are carried over powerline carrier channels utilizing the powerlines themselves to convey intelligence from one station to another. In order to insure that the described automatic station operation is possible, powerline carrier channels must be periodically tested to confirm their integrity.
In the past, powerline carrier channel testing has often required the presence of personnel at both ends of a powerline between which the carrier channel test is to be effected. Where prior procedures and structures have permitted testing of a powerline carrier channel from a single location, testing has usually still required a test operator at the location, and has been effected through a plurality of mechanical contactors and the like. Such powerline carrier channel test equipment and procedures have caused many false powerline carrier channel faults to be indicated, requiring investigation of each false fault indication. Moreover, procedures for testing powerlines having more than two ends with the equipment and methods of the past have been particularly complicated, and therefore undesirable.
Manual tests performed by operators in the past have been expensive, logistically difficult, and not easily repeated on a frequent schedule. More recent automatic testing equipment, including mechanical clocks, a plurality of mechanical contacts, etc., have provided automatic testing only on a rigid schedule.
Prior art powerline carrier channel test structures have not permitted variable programming of automatic test times. Nor have they accommodated a remote supervisory control interface so that tests may be made at will from a remote location and/or manually in conjunction with but separate from scheduled automatic testing.